Which Mussarnik gave the following pshat?
Sukkah 49 b says "Whoever has chen (favor) upon him must be a yirei shamayim (fears heaven). The Gemara says (Megilla 13a) that Esther was green-tinged (probably means pale) but a strand of chesed was drawn to her. When Esther "found favor and and kindness (chen v'chesed) in the eyes of Achashveirosh (see 5:2; this actual phrase is from 2:17). Esther won over Achashveirosh when she was found favorable in his eyes through her Yiras Shamayim. Thereofre she fasted three days, in order to strengthen her yiras shamayim, and through that "she found favor in the eyes of Achashveirosh."
Who do you think? Rav Yisrael Salanter? The Mashgiach Rav Yerucham Levovotiz of Mir? The Alter of Slabodka?
Rav Yosef Dov (Yoshe Ber) Soloveichik, in Reshimos Shiurim to Sukkah 49b.
Here is a Halachik pshat in Megilla I offered last year.